Green-Manures on Heavier Lands 



253 



of humus than 

 would be possible 

 when but one of 

 these crops were 

 grown. With an 

 abundance of the 

 mineral constitu- 

 ents the two crops 

 may, without dif- 

 ficulty, add a hun- 

 dred pounds or 

 more of nitrogen 

 to the soil per acre. 

 Green - manures 

 on loams and clay 

 soils. While best 

 adapted for light, 

 sandy soils, sys- 

 tems of green-ma- 

 nuring have also 

 been successfully 

 followed on heavier 

 loams or clay soils. 

 Lupins, seradella, 

 yellow, red and 

 crimson clover, 

 field - peas, horse- 

 beans and vetches, 

 have been em- 

 ployed on such 

 soils with marked 



Fig. 46. Tubercles on the roots of a young alfalfa 

 plant. 



